Update Product and Add Types in Payments

[armando-rodriguez-cko]

Description:

This PR updates the Product class and enhances the ProductType enumeration to introduce additional product types and improve handling of payment product details.

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Key Changes:

Product.java Updates:

• Added a new field:
  • ProductType type – Specifies the type of product (e.g., digital, physical, etc.).
• Added new field annotations:
  • @SerializedName("service_ends_on") Instant serviceEndsOn – Specifies the service end date for applicable products.

ProductType.java Enhancements:

• Introduced new product types:
  • DIGITAL – Representing digital products.
  • PHYSICAL – Representing physical goods.

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Impact:

• Improved Flexibility: Supports more diverse product types, ensuring compatibility with broader use cases like physical goods, digital items, and invoices.
• Enhanced Serialization: Added annotations ensure accurate serialization for service-related fields.

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Additional Notes:

• Changes align with expanding requirements for payment handling in the Checkout.com SDK.
• Backward compatibility maintained while extending product capabilities.